Ignition system

ABSTRACT

A photo optical ignition system configured to mount within most conventional distributors so that the circuits are protected from unwanted electromagnetic radiation. Copper shielding provides additional protection from electromagnetic radiation and a special voltage control circuit immunizes the system from voltage variations in the vehicle power circuits.

United States Patent 1 Wernet, Jr.

[ Apr. 30, 1974 IGNITION SYSTEM 3,438,362 3/1969 Clybome 1233/1465 [76] Inventor: William A. Wernet, Jr., 407 1st OTHER PUBLICATIONS South South Paul Electronics Australia, September, 1970; An All Elec- 55075 tronic Ignition System" by George Hughes [22] Filed: Mar. 23, 1972 Primary Examinerl..aurence M. Goodridge [211 App! 237407 Assistant ExaminerRonald B. Cox

Attorney, Agent, or Firm-William A. Wernet, Jr. [52] US. Cl. 123/148 E, 123/148 F [51] Int. Cl. F02p H 57 ABSTRACT [58] Field of Search 123/148 E, 32 EA A photo Optical ignition System configured to mount 56 R f Cted within most conventional distributors so that the cir- 1 e erences I cuits are protected from unwanted electromagnetic UNITED STATES PATENTS radiation. Copper shielding provides additional pro- 3,472,2l6 /1969 Clyborne 123/148 E {action from electromagnetic radiation and a special 3-654905 4/1972 Mennesso" 123/3215A voltage control circuit immunizes the system from 3646'926 3/1972 Plume [23/148 E voltage variations in the vehicle power circuits. 3,368,539 2/1968 Kldwell l23/l48 3,422,804 H1969 Van Mastrigt 1323/1424 4 Claims, 4 Drawing Figures Z2 Z0. 3 "I I K I I 6/ 1 i Z4 m IGNITION SYSTEM BACKGROUND OF THE INVENTION In the prior art it is common knowledge that practically all cars and trucks on the road today use spark plug fired internal combustion engines. The spark plugs in these engines are fired at predetermined times by means of a coil which coil is in tum'activated by a set of cam operated points mounted within a distributor. The distributor also operates to select the particular spark plug which the coil is firing at any given moment. These distributors are quite similar in construction throughout the industry and may therefore be said to be virtually standardized.

The difficulties encountered in the operation of points in a distributor are well known to those skilled in the art. Points invariably become dirty and corroded and must be continually adjusted and replaced. In addition, the inherent mechanical characteristics of the switching points make them change their time of switching so that even immediately after a tune up the vehicle starts to lose performance due to slight misadjustments from the ideal timing. Ignition systems using points have always had these problems and as a consequence, in the prior art many attempts have been made to switch over to electronic switching devices to do away with the cam driven mechanically operated points.

Prior art systems have included optical and magnetic pickups designed to generate a pulse in response to the position of some indicator on the distributor rotor shaft. This electrical pulse is then amplified and used to trigger a charge of electricity to the spark plugs. None of these prior art systems has worked particularly well due to the difficulty of achieving a reliable switching means to activate the spark plug circuit involved. One of the most serious problems in the prior art revolves around the circuitry used to generate the electronic switching. Due to thespark plugs and other electrical equipment in the typical vehicle there is a great amount of electromagnetic noise being generated in the proximity of the distributor, This noise is picked up by the electronic switching circuits and operates to degrade the performance of the circuits.

Another problem is that most prior art systems must use magnetic pickups. In the case of magnetic pickups it is always difficult to establish a clearly defined point at which the magnetic signal will cause a pulse to be generated. Optical systems and pickups have been found to be much more accurate in establishing an exact point at which to trigger the spark plug. However, optical systems suffer from the disadvantage that the light source varies greatly in intensity depending upon variations in the current supplied to the source which variations can result from a number of conditions. Poor battery condition or cold weather can change the amount of current available to drive the photo source. When the automobile is being started the consequent draw of current greatly reduces the voltage available for the ignition photo source. If the generating system of the vehicle fails it may be necessary to drive a significant distance on the battery alone thus causing a great reduction in the amount of voltage available to drive the photo source. On the other hand faulty generating systems can produce too high a voltage and burn the light source out. My invention overcomes these difficulties as described below.

SUMMARY OF THE INVENTION Briefly, my invention contemplates using an optical system'with a chopper disc on the distributor rotor to pass precisely timed pulses of light to a photo transistor. The resultant photo transistor signal may be amplified and used to trigger the spark plugs. A special voltagecontrol circuit is used to make the light source independentof any variation in the voltage of the vehicle circuits. To protect the photo transistor circuits from stray outside electromagnetic radiations the entire apparatus is miniaturized onto a circuit board which is configured to fit within the confines of the distributor so that there are no electrical leads long enough to pick up any stray electromagnetic radiation of any significant intensity. Because the system is miniaturized to fit within the conventional distributor it is adaptable to be mounted on almost any of the distributors in use today. Additional electromagnetic protection is provided by copper shielding mounted on the circuit boards which copper shielding is suitably grounded. It may therefore be seen that it is an object of my invention to provide an ignition system which is highly accurate, immune to outside electromagnetic interference, and which will not degrade in performance due to long use. It is a further object of my invention to provide a photo optical ignition system which is not affected, by variations in the voltage supplied by the vehicle electrical system. It is still another object of my invention to provide a photo optical ignition system which is adapted to conventional distributors and may be contained totally within most distributors on the market today. Other objects and advantages will become apparent to those skilled in the art upon consideration of the following description and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic side view of the distributor with the cover cut away so as to indicate the photo optical ignition system mounted therein.

FIG. 2 is another schematic view of the distributor showing the photo optical ignition system as it would appear from the right in FIG. 1 and also having the cover cut away for increased clarity.

FIG. 3 is a top view of the apparatus of FIG. 2 showing just the essential internal components and omitting the cover completely for clarity.

FIG. 4 is a circuit diagram of the electronic components mounted within the distributor demonstrating the unique voltage control circuit.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring simultaneously to FIGS. 1, 2 and 3 a distributor is schematically shown having a base support member 10. Member 10 usually comprises a generally disc-shaped member with a rim 11, as shown in FIG. 3, mounted upon a housing shaft 14. Shaft 14 is inserted into the engine of the vehicle so that a gear 16 engages the rotating gears inside the engine, usually at the cam shaft. In this way gear 16 drives a rotor shaft 18 inside shaft 14 at a speed proportional to the speed of the enginefA rotatable mounting plate 20 is generally positioned on a hub 24 so as to be rotatable about shaft 18 to a limited degree. This rotation is usually controlled by suitable external devices so as to achieve an advance or retard in the ignition timing in accordance with principles well known to those skilled in the art. For the purposes of clarity the advance and retard mechanisms are omitted in the instant application although it will be understood later that the photo optical ignition system of the present invention is mounted on and therefore rotatable with plate 20 so as to be subject to this advance and retard characteristic. A cam 22 mounted on rotor shaft 18 normally drives a spring loaded set of mechanical ignition points which are normally mounted on plate 20. The present invention however, eliminates the necessity for these points by providing a photo optical system as will be described hereinafter.

To adapt the photo optical ignition system of the present invention to the conventional distributor a radiation chopping disc 26 is secured by any suitable means to rotor shaft 18. In the preferred embodiment disc 26 rests on the top of cam 22. The disc may be held in place by a friction fit, glue, small screws or any other suitable approach well know to those skilled in the art. Disc 26 is provided with a number of openings 27 about its periphery. These openings depend in number on the number of spark plugs used in the engine. A pair of screws 30 along with suitable nuts 31 and spacers 34 are used to mount a primary circuit board 32 and a secondary circuit board 40 onto plate 20. A radiation source 42 which may generate any frequency of light desired is mounted through board 40 and a radiation detector 44 is mounted on circuit board 32 in such a position that the radiation or light from source 42 reaches detector 44 in pulses caused by the passage of openings 27 in disc 26. In the preferred embodiment a photo transistor is used for detector 44 which uses the light pulses to generate an electrical pulse which is amplified by the circuitry mounted on circuit board 32 and used to trigger the spark plugs. This circuit is described in greater detail at a later point.

In the drawings several electronic components numbered 60, 61, 62 and 63 are schematically shown affixed to circuit board 32. These components are connected together either by direct connection on the reverse side of the circuit board 32 or by a printed circuit in a manner well known to those skilled in the art. The exact components and location of components is not essential to the inventive concept employed in this invention. Consequently, only a few of the components are schematically shown. The primary principle involved is that the total circuit, which is described in detail later, is mounted as compactly as possible on circuit boards within the confines of the distributor. As a result, the leads between the components are so short that stray electromagnetic radiation has no adverse effeet on the circuit operation. For the same reasons the leads 70 and 70' from light source 42 are caused to be as short as possible. In the preferred embodiment they are routed directly to a pair of connecting tabs 53 and 54 which are visible in FIG. 3. Suitable connections are then made from tabs 53 and 54 to the circuitry on board 32. These connections are omitted in the drawings for clarity.

In order to provide even additional electromagnetic shielding thin copper sheets 50, 51 and 52 are mounted on both sides of mounting board 40. Sheets 50 and 52 are grounded by virtue of their contact with spacers 34 and screws 30. Copper sheet 51 is grounded through copper sheet 52 by means of their common contact with the metal housing for source 42 although other arrangements will work equally well. The use of these copper sheets directly above the circuit provides additional electromagnetic shielding from the spark plugs which are connected to the distributor at the top of cover 12. These connections are standard in the industry and therefore are not shown in the drawings.

Referring to FIG. 4 the circuit used in the preferred embodiment is schematically illustrated. Radiation source 42 comprises a diode source which is supplied current by a constant current regulator circuit incorporating a transistor 66 and a resistor 69. Transistor 66 is held at a constant level by a voltage signal derived from a Zener diode 67 which receives current through a resistor 65 from the power terminal 80. Thus, the current supply to light source 42 is held constant and immune from too high or too low supply voltages.

Photo transistor 44 is coupled to the power terminal 80 by a resistor 71 and to ground by a resistor 72. The output of photo transistor 44 is taken from the emitter to constitute an emitter follower circuit. This output is coupled to a two stage amplifier comprising transistors 73 and 77 and resistors 74, 75 and 76. The final output is derived at terminal 78. The circuits of my invention may be interfaced with any type of spark triggering circuits by the correct selection of transistor 77 and resistor 76.

I claim:

1. An ignition timing system adaptable to conventional distributors for internal combustion engines comprising:

a radiation chopping disc adapted to be mounted for rotation on the rotor shaft of the distributor, said disc provided with openings about the periphery thereof spaced in proper positions to pass radiation therethrough at a frequency appropriate to the number of spark plugs in the engine to which the system is applied; plurality of threaded members extending from and mounted on the base of the conventional distributor, which base is normally used to mount the conventional points of the distributor, said threaded members extending past the edge of said disc and carrying first and second circuit boards which boards extend generally perpendicular from the threaded members to locations proximate each side of said disc; radiation source mounted on one side of said disc on said first circuit board and connected to a voltage control circuit so as to receive a constant voltage therefrom said control circuit comprising a transistor connected in series with a resistor and said source so as to regulate the flow of current therethrough, said transistor controlled by a voltage signal derived from a Zener diode;

a radiation detector on the other side of the disc and on said second circuit board positioned to receive the radiation from said source which passes through the openings in said disc;

an amplifying circuit formed on the second circuit board and connected to said detector operable to generate an electrical pulse in response to the reception of radiation by said detector, said source, detector, and circuit being positioned within the confines of the cover of the conventional distributor.

2. The system of claim 1 including conductive shielding material on both sides of said first circuit board, which material is grounded so as to provide an electro- 4. The apparatus of claim 3 in which said control cir- 6 cuit comprises a transistor connected in series with a resistor and said source so as to regulate the flow of current therethrough, said transistor controlled by a voltage signal derived from a Zener diode. 

1. An ignition timing system adaptable to conventional distributors for internal combustion engines comprising: a radiation chopping disc adapted to be mounted for rotation on the rotor shaft of the distributor, said disc provided with openings about the periphery thereof spaced in proper positions to pass radiation therethrough at a frequency appropriate to the number of spark plugs in the engine to which the system is applied; a plurality of threaded members extending from and mounted on the base of the conventional distributor, which base is normally used to mount the conventional points of the distributor, said threaded members extending past the edge of said disc and carrying first and second circuit boards which boards extend generally perpendicular from the threaded members to locations proximate each side of said disc; a radiation source mounted on one side of said disc on said first circuit board and connected to a voltage control circuit so as to receive a constant voltage therefrom said control circuit comprising a transistor connected in series with a resistor and said source so as to regulate the flow of current therethrough, said transistor controlled by a voltage signal derived from a Zener diode; a radiation detector on the other side of the disc and on said second circuit board positioned to receive the radiation from said source which passes through the openings in said disc; an amplifying circuit formed on the second circuit board and connected to said detector operable to generate an electrical pulse in response to the reception of radiation by said detector, said source, detector, and circuit being positioned within the confines of the cover of the conventional distributor.
 2. The system of claim 1 including conductive shielding material on both sides of said first circuit board, which material is grounded so as to provide an electromagnetic shield for the circuits on said second circuit board.
 3. The apparatus of claim 2 including a voltage control circuit connected to provide a constant voltage to said radiation source.
 4. The apparatus of claim 3 in which said control circuit comprises a transistor connected in series with a resistor and said source so as to regulate the flow of current therethrough, said transistor controlled by a voltage signal derived from a Zener diode. 